U.S. patent application number 12/718779 was filed with the patent office on 2010-06-24 for liquid crystal projector apparatus and cooler.
This patent application is currently assigned to NEC VIEWTECHNOLOGY, LTD.. Invention is credited to Motoyasu UTSUNOMIYA.
Application Number | 20100157176 12/718779 |
Document ID | / |
Family ID | 34616762 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100157176 |
Kind Code |
A1 |
UTSUNOMIYA; Motoyasu |
June 24, 2010 |
LIQUID CRYSTAL PROJECTOR APPARATUS AND COOLER
Abstract
A liquid crystal projector apparatus has a liquid crystal unit
having a liquid crystal panel for modulating light, an incident
side polarizing plate and an exit side polarizing plate disposed in
front of and behind the liquid crystal panel along the optical
axis, respectively, a first holder member for holding the liquid
crystal unit, a first heat exchanger disposed in close proximity to
the first holder member for dissipating heat generated by the
liquid crystal unit and then conducted to the first holder member
using a coolant liquid which passes through a first channel formed
inside the first heat exchanger, a pump for circulating the coolant
liquid, and a radiator for cooling the coolant liquid.
Inventors: |
UTSUNOMIYA; Motoyasu;
(Tokyo, JP) |
Correspondence
Address: |
YOUNG & THOMPSON
209 Madison Street, Suite 500
Alexandria
VA
22314
US
|
Assignee: |
NEC VIEWTECHNOLOGY, LTD.
Tokyo
JP
|
Family ID: |
34616762 |
Appl. No.: |
12/718779 |
Filed: |
March 5, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11001320 |
Dec 2, 2004 |
7703927 |
|
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12718779 |
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Current U.S.
Class: |
349/5 |
Current CPC
Class: |
G02F 1/133385 20130101;
H04N 9/3144 20130101; G03B 21/16 20130101 |
Class at
Publication: |
349/5 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 2, 2003 |
JP |
2003-402880 |
Claims
1. A liquid crystal projector apparatus comprising: a liquid
crystal panel for modulating light; an incident side polarizing
plate and an exit side polarizing plate disposed in front of and
behind said liquid crystal panel along an optical axis,
respectively; a first holder member for holding said liquid crystal
panel; a first heat exchanger disposed in close proximity to said
first holder member for dissipating heat generated by said liquid
crystal panel, said incident side polarizing plate, or said exit
side polarizing plate, and then conducted to said first holder
member, said first heat exchanger including a first channel formed
therein for passing a coolant liquid therethrough for dissipating
the heat; a circulator constructed and arranged to circulate said
coolant liquid; and a coolant liquid cooler; wherein: said first
heat exchanger is disposed on a surface of said first holder member
opposite to a surface for holding said liquid crystal panel, said
incident side polarizing plate, and said exit side polarizing
plate, said first channel passes through positions substantially
opposite to positions at which said liquid crystal panel, said
incident side polarizing plate, and said exit side polarizing plate
are held by said first holder member, said liquid crystal panel
comprises a plurality of liquid crystal panels for modulating
different color light, respectively, said first channel first
passes through the position substantially opposite to the position
at which the liquid crystal panel generating the largest amount of
heat among said plurality of liquid crystal panels is held by said
first holder member, said plurality of liquid crystal panels have
three liquid crystal panels for modulating blue light, green light,
and red light, respectively, and said first channel passes through
positions, in an order of the position substantially opposite to
the position at which said liquid crystal panel for modulating blue
light is held by said first holder member, the position
substantially opposite to the position at which said liquid crystal
panel for modulating green light is held by said first holder
member, and the position substantially opposite to the position at
which said liquid crystal panel for modulating red light is held by
said first holder member.
2. The liquid crystal projector apparatus of claim 1, further
comprising: a second holder member for holding said liquid crystal
panel, said incident side polarizing plate, and said exit side
polarizing plate between said first holder member and said second
holder member; and a second heat exchanger disposed in close
proximity to said second holder member for dissipating heat
generated by said liquid crystal panel, said incident side
polarizing plate, or said exit side polarizing plate, and then
conducted to said second holder member; wherein: said second heat
exchanger includes a second channel formed therein for passing a
coolant liquid therethrough for dissipating the heat, said second
heat exchanger is disposed on a surface of said second holder
member opposite to a surface for holding said liquid crystal panel,
said incident side polarizing plate, and said exit side polarizing
plate, said second channel passes through positions substantially
opposite to positions at which said liquid crystal panel, said
incident side polarizing plate, and said exit side polarizing plate
are held by said second holder member, and said second channel
first passes through the position substantially opposite to the
position at which the liquid crystal panel generating the largest
amount of heat among said plurality of liquid crystal panels is
held by said second holder member.
3. A cooler for cooling a plurality of heat-generating objects that
generate different amounts of heat from one another, comprising: a
first holder member for holding the plurality of heat-generating
objects; a first heat exchanger disposed in close proximity to said
first holder member for dissipating heat generated by the
heat-generating objects, and then conducted to said first holder
member, said first heat exchanger including a first channel formed
therein for passing a coolant liquid therethrough for dissipating
the heat; a circulator constructed and arranged to circulate said
coolant liquid; and a coolant liquid cooler; wherein: said first
heat exchanger is disposed on a surface of said first holder member
opposite to a surface for holding the heat-generating objects, said
first channel passes through positions substantially opposite to
positions at which the heat-generating objects are held by said
first holder member, said first channel first passes sequentially
through positions opposite the plurality of heat-generating objects
in an order that corresponds to the amount of heat generated by the
heat-generating objects, beginning with the heat-generating object
that generates the greatest amount of heat, and ending with the
heat-generating object that generates the least amount of heat.
4. The cooler of claim 3, wherein said first channel is arranged to
have a width that differs as said first channel first passes
sequentially through positions opposite the plurality of
heat-generating objects, such that the width of the first channel
is greatest as the first channel passes opposite the
heat-generating object that generates the greatest amount of heat,
and the width of the first channel is least as the first channel
passes opposite the heat-generating object that generates the
smallest amount of heat.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a liquid crystal projector
apparatus for projecting an image using a liquid crystal panel, and
more particularly, to a structure and method for cooling the liquid
crystal panel and polarizing plate.
[0003] 2. Description of the Related Art
[0004] Liquid crystal projector apparatuses have been dramatically
improved in image quality, resulting from an increase in the
luminance of a light source, refinement of liquid crystal light
valves, and the like, and are now utilized widely from home theater
applications to business presentations.
[0005] FIG. 1 illustrates the basic configuration of a liquid
crystal projector apparatus. Liquid crystal projector apparatus 1
comprises three optical systems including illumination optical
system 2, color separating optical system 7, and light composing
optical system 13.
[0006] Illumination optical system 2 comprises light source 3
including a high luminance lamp such as a metal halide lamp, an
ultra-high pressure mercury lamp, or the like; reflector 4 for
reflecting light from light source 3; optical integrators 5a, 5b
each for uniformarizing a luminance distribution of reflected light
from reflector 4; and polarization beam splitter (PBS) 6 for
transforming randomly polarized light from light source 3 into
linearly polarized light.
[0007] Color separating optical system 7 comprises dichroic mirrors
8a, 8b each for separating an entire light flux from illumination
optical system 2 into individual color light fluxes of red (R),
green (G), and blue (B) and directing the separated color light
fluxes to respective liquid crystal panels corresponding thereto;
reflective mirrors 9a, 9b, 9c; and relay lenses 10a, 10b.
[0008] Light composing optical system 13 comprises light modulator
14 for modulating the respective color light fluxes applied from
color separating optical system 7 in accordance with given image
information; color combiner prism 15 for combining the modulated
color light fluxes; and projection lens 16 for projecting the
combined light flux onto a screen.
[0009] Among the foregoing components, light modulator 14 in light
composing optical system 13 comprises liquid crystal panels 17a,
17b, 17c, each of which is a transmission type display device;
incident side polarizing plates 18a, 18b, 18c each disposed on the
incident side of liquid crystal panel 17a, 17b, 17c; and exit side
polarizing plates 19a, 19b, 19c each disposed on the exit side of
liquid crystal panel 17a, 17b, 17c. Since a TN (Twisted Nematic)
liquid crystal panel can exclusively handle a particular linearly
polarized light component, respective color light fluxes from color
separating optical system 7 are uniformly directed in a
predetermined polarization direction (P-polarized light) by
incident side polarizing plates 18a, 18b, 18c. After the
P-polarized light is modulated by liquid crystal panels 17a, 17b,
17c, S-polarized light components of the modulated light is only
allowed to pass through exit side polarizing plates 19a, 19b,
19c.
[0010] While the optical configuration shown herein is associated
with a three-plate type liquid crystal projector apparatus which
separates light from a light source into three primary colors which
are individually modulated by three liquid crystal panels, a light
modulator in a similar configuration is also used in a
low-luminance, inexpensive, single-plate type liquid crystal
projector apparatus which employs only one liquid crystal
panel.
[0011] In light modulator 14 in the configuration as described
above, incident side polarizing plates 18a, 18b, 18c and exit side
polarizing plates 19a, 19b, 19c tend to generate heat because each
of these plates allows only polarized light in a single axial
direction to pass therethrough and shields (absorbs) the remaining
polarized light. Likewise, liquid crystal panels 17a, 17b, 17c
involve the generation of heat when in operation, because
transmitted light is shielded in a lattice-shaped wire called a
black matrix which surrounds pixels on the panel. Liquid crystal
panels 17a, 17b, 17c, incident side polarizing plates 18a, 18b,
18c, and exit side polarizing plates 19a, 19b, 19c are often made
of organic materials, so that if these components are irradiated
with short-wavelength light or exposed to a high-temperature
environment for a long time, their functions are significantly
compromised due to damaged panel alignment films, lowered polarized
light selection characteristics, and the like. Such functional
damages will result in a shorter lifetime of products, an increased
running cost caused by frequent replacements of damaged components,
a degradation in combined projection images due to variations in
the respective color light characteristics. Therefore, some
countermeasures must be taken against heat for these light
modulators.
[0012] The following description will be made on a cooling method
which has been conventionally employed for limiting a rise in
temperature of the incident side polarizing plates, exit side
polarizing plates, and liquid crystal panels (hereinafter these
members are collectively called "liquid crystal unit 23").
[0013] FIGS. 2A, 2B are explanatory diagrams generally illustrating
an exemplary method of cooling a liquid crystal unit based on a
forced air cooling scheme. FIG. 2A illustrates a perspective view
of the cooling structure unit, wherein cooling fan 20, which
comprises an axial fan or a radial fan, takes external air from a
suction port of a liquid crystal projector housing (not shown), and
introduces cooling air from an outlet port of cooling fan 20 to
duct opening 22 beneath liquid crystal unit 23 through duct 21. As
illustrated in FIG. 2B, incident side polarizing plates 18a, 18b,
18c, liquid crystal panels 17a, 17b, 17c, and exit side polarizing
plates 19a, 19b, 19c, which make up liquid crystal unit 23, are
spaced apart from one another such that the cooling air passes
upward through gaps therebetween to take the heat on surfaces to be
cooled, i.e., cool the members. An air flow, which has been heated
by the heat exhausted from liquid crystal unit 23, is emitted to
the outside of the housing from an exhaust port of the liquid
crystal projector housing.
[0014] Other than the air cooling scheme, a liquid cooling scheme
is also used for the liquid crystal unit. The liquid cooling scheme
involves immersing heat-generating members of the liquid crystal
unit in a coolant container filled with a coolant liquid to
transport the heat generated in the liquid crystal unit through
natural convection of the coolant liquid which has a high heat
conductivity, and is disclosed, for example, in specification etc.
of Japanese Patent Laid-open Publication No. 2002-214596. FIGS. 3A,
3B are conceptual diagrams illustrating an exemplary liquid cooling
structure applied for cooling an exit side polarizing plate. In
FIG. 3A, incident side polarizing plate 18d, liquid crystal panel
17d, exit side polarizing plate 19d, and color combiner prism 15
are spaced apart from one another in an order in which light
travels therethrough. As illustrated in a partially enlarged view
of FIG. 3B, exit side polarizing plate 19d is adhered to
transparent substrate 30a of a cooling element, and cooled by the
cooling element. The cooling element comprises metal frame 24a; two
transparent substrates 30a, 30b adhered to openings of metal frame
24a with a gap therebetween; and coolant liquid 31 filled in an
internal space defined between transparent substrates 30a, 30b.
[0015] FIG. 4 is a conceptual diagram illustrating another prior
art liquid cooling structure which is disclosed in specification
etc. of Japanese Patent Laid-open Publication No. 2002-357803.
Liquid crystal panel 17e and exit side polarizing plate 19e are
contained within metal frame 24b such that they are spaced apart
from each other, and coolant liquid 31 is filled and enclosed in
the internal space defined by liquid crystal panel 17e and exit
side polarizing plate 19e to simultaneously cool liquid crystal
panel 17e and exit side polarizing plate 19e.
[0016] Either of the foregoing examples takes heat from members to
be cooled through a coolant liquid, transports the heat to a metal
frame by circulating the coolant liquid through convection, and
cools the metal frame together with other liquid crystal unit
members which are not immersed in the coolant liquid, by an air
cooling fan disposed outside to dissipate the heat.
[0017] As disclosed in specification etc. of Japanese Patent
Laid-open Publication No. 2003-195421, a method of improving
cooling capabilities of a liquid crystal panel itself, which forms
part of a liquid crystal unit, bonds a heat dissipating plate(s) or
the like made of a transparent thin plate material having a thermal
conductivity higher than liquid crystal panel components on one or
both of the incident surface and exit surface of a liquid crystal
panel. With the plate having a high thermal conductivity bonded to
a heat generating surface, thermal diffusion on the panel surface
is increased to improve the cooling capabilities.
[0018] Further, in a conventional liquid crystal projector
apparatus, as shown in specification etc. of Japanese Patent
Laid-open Publication No. 2003-75912, a liquid crystal panel, which
forms part of a liquid crystal unit, is often provided with an
adjusting function (adjustments of the optical axes) for
adjustments in the vertical, horizontal, and rotating directions to
permit alignments among respective pixels on the panel for a
registration adjustment to precisely superimpose projected images
from liquid crystal panels corresponding to the respective colors
on a screen. FIGS. 5A, 5B illustrate an exemplary method of
supporting a liquid crystal panel which can be optically adjusted.
As illustrated in FIG. 5A, liquid crystal panel 17c is supported at
a location spaced apart from color combiner prism 15. As
illustrated in FIG. 5B which is a detailed cross-sectional view of
the supporting structure, liquid crystal panel 17c is securely held
by fixture 26c, and four corners of fixture 26c are supported at
four points by holder protrusions 27, and are securely adhered
after the optical axis has been adjusted. As a result, liquid
crystal panel 17c itself is supported as if it were fixed in the
air. To improve heat dissipation capabilities of this type of
liquid crystal panel, a method has been disclosed for fixing the
liquid crystal panel (fixture) and panel fixing frame (holder
protrusions) with a thermally conductive adhesive resin.
[0019] In the prior art liquid crystal projector apparatuses
described above, first of all, the following problems have been
recognized in the liquid crystal projector apparatus which employs
a forced air cooling scheme using a cooling fan.
[0020] A first problem is noise. A demand for higher luminance of
liquid crystal projector apparatuses drives an increase in lamp
power, whereas liquid crystal panels tend to be reduced in size in
response to a demand for a reduction in the size of the
apparatuses, necessarily resulting in an increase in the density of
light flux incident on the liquid crystal unit which suffers an
increased heat load. In the forced convection using a cooling fan,
since its average thermal conductivity is proportional to 1/2 power
of wind speed, the wind speed must be increased for effectively
dissipating heat generated in the liquid crystal unit. While there
are two methods contemplated for increasing a cooling wind speed,
i.e., the employment of a larger fan, and an increase in the wind
speed, the former method is not compatible with the demand for a
reduction in size, and may often encounter difficulties in
physically installing a larger fan in a housing. Therefore, a small
fan is rotated at a higher speed to increase the amount of supply
air to ensure the cooling capabilities. However, an increase in the
rotational speed of the fan causes increased noise which
exacerbates the comfort of the user.
[0021] A second problem is the reliability. When a light modulator
is cooled down through forced air cooling in a liquid crystal
projector apparatus, a problem is caused by dust particles which
are mixed in cooling air taken from external air. A liquid crystal
light valve has a pixel size of 26 .mu.m square in a 1.3'' XGA, so
that if dust particles of a size on the order of several tens of
micrometers stick on an imaging surface of the panel, enlarged
shadows of the dust particles are projected onto a screen together
with an image to degrade the image quality. To solve this problem,
a finer filter may be attached to a suction port for enhancing a
filtering function, but will cause another problem of an increased
loss of suction pressure of the fan to cause a reduced amount of
supply air and a resulting failure in providing sufficient cooling
performance.
[0022] On the other hand, a liquid crystal projector apparatus
which employs a liquid cooling scheme implies the following
problems. A first problem is the image quality. When a coolant
liquid is filled between components of a liquid crystal unit (for
example, between liquid crystal panel 17e and exit side polarizing
plate 19e in FIG. 4), a liquid layer intervenes in a light
transmission space, and therefore causes disturbed polarization of
light which transmits the liquid layer due to variations in coolant
density arising from generation of air bubble and thermal
transportation, and due to non-uniform convection resulting
therefrom, resulting in discrepancy in image information which
passes through the exit side polarizing plate, and a degraded
quality of a projected image.
[0023] A second problem is the reliability and mountability. Since
the heat is dissipated from the liquid crystal unit through the
encapsulated coolant liquid, the coolant liquid repeats expansion
and contraction as it is used. While a coolant container is
provided with a pressure adjusting mechanism for accommodating the
expansion and contraction of the coolant liquid, a pressure
adjusting member may be damaged in a long-term service to possibly
cause a leak of the coolant liquid. In addition, a complicated
sealing structure and pressure adjusting structure of the coolant
container could significantly impair the ease of assembly of an
optical engine.
[0024] Further, the aforementioned liquid crystal projector
apparatus of the type which fixes a liquid crystal panel by a
holder member in the air has problems in that the connection areas
of the protrusions which support the liquid crystal panel at four
points are not sufficient to absorb the heat generated in the
liquid crystal panel, and that a sufficient thermal connection
cannot be ensured due to limitations imposed by the heat conducting
performance of the adhesive resin. In addition, when the liquid
crystal panel is fixed by the holding mechanism of the holder
member in a manner similar to the other polarizing plates, the
liquid crystal panel can be affected by the rigidness of the
holding mechanism, resulting in the possibility in going out of
alignment during assembling or in operation. However, it is
difficult to accomplish a thermal connection without affecting the
posture of the liquid crystal panel fixed in the air.
SUMMARY OF THE INVENTION
[0025] It is an object of the present invention to provide a method
and mechanism for cooling a liquid crystal unit, which has
sufficient cooling capabilities with low noise and high
reliability.
[0026] It is another object of the present invention to provide a
liquid crystal projector apparatus and a method of cooling the
liquid crystal projector apparatus which accomplishes a higher
luminance and a silenced operation, and has a long lifetime and
high reliability.
[0027] A liquid crystal projector apparatus according to the
present invention includes a liquid crystal panel for modulating
light, an incident side polarizing plate and an exit side
polarizing plate disposed in front of and behind the liquid crystal
panel along an optical axis, respectively, a first holder member
for holding the liquid crystal panel, incident side polarizing
plate, and exit side polarizing plate, and a first heat exchanger
disposed in close proximity to the first holder member for
dissipating heat generated by the liquid crystal panel, incident
side polarizing plate, or exit side polarizing plate and conducted
to the first holder member.
[0028] With the foregoing configuration, heat generated by the
liquid crystal panel, incident side polarizing plate, and exit side
polarizing plate is transferred to the first holder member which
holds these components, and the heat is dissipated by the first
heat exchanger in close proximity to the first holder member, thus
eliminating the need for a forced air cooling mechanism for
dissipating such heat the problems of dust particles sticking to
the liquid crystal unit, which can cause a problem in an air
cooling scheme, and a degraded image quality are reduced. In
addition, the liquid crystal projector apparatus excels in silenced
operation because it does not need a large capacity air cooling
fan.
[0029] In the liquid crystal projector apparatus of the present
invention, the first heat exchanger may include a first channel
formed therein for passing a coolant liquid therethrough for
dissipating the heat, and the liquid crystal projector apparatus
may further include circulating means for circulating the coolant
liquid, and coolant liquid cooling means for cooling the coolant
liquid. This liquid cooling system can accomplish higher efficiency
of cooling.
[0030] The first heat exchanger may be disposed on a surface of the
first holder member opposite to a surface for holding the liquid
crystal panel, incident side polarizing plate, and exit side
polarizing plate, and the first channel passes positions
substantially opposite to positions at which the liquid crystal
panel, incident side polarizing plate, and exit side polarizing
plate are held by the first holder member. Accordingly, since the
heat from the liquid crystal panel etc. is dissipated through the
first holder member and first heat exchanger, the optical system is
not basically affected by the coolant liquid, and therefore will
not suffer from a degraded image quality.
[0031] A method of cooling a liquid crystal projector apparatus
according to the present invention relates to a liquid crystal
projector apparatus having a liquid crystal panel for modulating
light, an incident side polarizing plate and an exit side
polarizing plate disposed in front of and behind the liquid crystal
panel along an optical axis, respectively, a first holder member
for holding the liquid crystal panel, the incident side polarizing
plate, and the exit side polarizing plate. The method comprising
the steps of: disposing a first heat exchanger in close proximity
to the first holder member; transferring heat generated by the
liquid crystal panel, the incident side polarizing plate, or the
exit side polarizing plate and then conducted to the first holder
member to the first heat exchanger through surface thermal
conduction between an outer surface of said first holder member and
an outer surface of said first heat exchanger; and dissipating the
heat transferred to the first heat exchanger.
[0032] With the foregoing configuration employing liquid cooling
system, a liquid crystal projector apparatus and a method of
cooling a liquid crystal projector apparatus of the present
invention enables cooling without introducing dust particles. The
apparatus and method eliminate the possibility of dust particles
sticking to the liquid crystal unit, degraded image quality. In
addition, the apparatus and method excels in silenced operation
because they do not need a large capacity air cooling fan.
[0033] As a result of employing the structure for exhausting heat
to a liquid cooling module through the holder member and heat
exchanger, rather than a structure which relies on the convection
for dissipating heat with a liquid crystal unit directly immersed
in a coolant liquid, the optical system is not basically affected
by the coolant liquid. Consequently, the liquid crystal projector
apparatus of the present invention will not suffer from a degraded
image quality, and excels in mountability.
[0034] Further, the cooling section, which is structured
independently of the liquid crystal unit, facilitates the
optimization for the designing of the heat exchanger, channel, etc.
Consequently, high cooling capabilities can be provided for a
particular condition in accordance with the configuration of the
liquid crystal unit and the amount of generated heat.
[0035] As will be appreciated from the foregoing, the present
invention can provide a liquid crystal projector apparatus which
has a long lifetime and high reliability while satisfying
requirements for a higher luminance and quietness, as well as a
cooling mechanism and a cooling method for the liquid crystal
projector apparatus.
[0036] The above and other objects, features and advantages of the
present invention will become apparent from the following
description with reference to the accompanying drawings which
illustrate examples of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a diagram generally illustrating the basic
configuration of an optical system in a conventional liquid crystal
projector apparatus;
[0038] FIGS. 2A, 2B are a perspective view and a cross-sectional
view, respectively, illustrating a liquid crystal unit cooling
structure (air cooling) of a conventional liquid crystal projector
apparatus;
[0039] FIGS. 3A, 3B are a perspective view and a cross-sectional
view, respectively, illustrating a liquid crystal unit cooling
structure (liquid cooling) of a conventional liquid crystal
projector apparatus;
[0040] FIG. 4 is a cross-sectional view illustrating a liquid
crystal unit cooling structure (liquid cooling) of a conventional
liquid crystal projector apparatus;
[0041] FIGS. 5A, 5B are a side view and a detailed view,
respectively, of a liquid crystal panel holder of a conventional
liquid crystal projector apparatus;
[0042] FIG. 6 is a perspective view illustrating an optical system
and a liquid crystal unit cooling system extracted from a liquid
crystal projector apparatus according to a first embodiment of the
present invention;
[0043] FIG. 7 is a perspective view of the liquid crystal projector
apparatus illustrated in FIG. 6, taken from another direction;
[0044] FIG. 8 is an exploded perspective view illustrating part of
the liquid crystal unit and liquid crystal unit cooling system in
the liquid crystal projector apparatus illustrated in FIG. 6;
[0045] FIG. 9 is a front view of the liquid crystal unit and liquid
crystal unit cooling system illustrated in FIG. 8;
[0046] FIG. 10 is a plan view illustrating the internal structure
of a heat exchanger for the liquid crystal projector apparatus
illustrated in FIG. 6;
[0047] FIGS. 11A, 11B are perspective views each illustrating part
of a liquid crystal unit and a liquid crystal cooling system in a
liquid crystal projector apparatus according to a second embodiment
of the present invention;
[0048] FIG. 12 is a front view of the liquid crystal unit and
liquid crystal unit cooling system of the liquid crystal projector
apparatus illustrated in FIGS. 11A, 11B;
[0049] FIG. 13 is a side view illustrating part of a liquid crystal
unit in a liquid crystal projector apparatus according to a third
embodiment of the present invention;
[0050] FIGS. 14A, 14B are side views each illustrating part of a
liquid crystal unit in the liquid crystal projector apparatus
according to the third embodiment of the present invention;
[0051] FIGS. 15A-15C are a side view, an enlarged side view, and a
perspective view, respectively, illustrating part of a liquid
crystal unit in a liquid crystal projector apparatus according to a
fourth embodiment of the present invention;
[0052] FIGS. 16A-16C are diagrams illustrating the configuration of
a holder member in the liquid crystal projector apparatus according
to the fourth embodiment of the present invention;
[0053] FIGS. 17A-17C are diagrams illustrating the configuration of
a heat exchanger in the liquid crystal projector apparatus
according to the fourth embodiment of the present invention;
[0054] FIGS. 18A-18C are diagrams illustrating the configuration of
a liquid crystal panel in a liquid crystal projector apparatus
according to a fifth embodiment of the present invention;
[0055] FIGS. 19A-19C are diagrams illustrating the configuration of
an exit side polarizing plate for use in a liquid crystal projector
apparatus according to a sixth embodiment of the present
invention;
[0056] FIG. 20 is a plan view illustrating the internal structure
of a heat exchanger in a liquid crystal projector apparatus
according to a seventh embodiment of the present invention;
[0057] FIG. 21 is a plan view illustrating the internal structure
of another heat exchanger in the liquid crystal projector apparatus
according to the seventh embodiment of the present invention;
[0058] FIG. 22 is a plan view illustrating the internal structure
of a further heat exchanger for the liquid crystal projector
apparatus according to the seventh embodiment of the present
invention;
[0059] FIGS. 23A-23C are a perspective view, a side view, and an
exploded perspective view, respectively, illustrating part of a
liquid crystal unit and a liquid crystal unit cooling system in a
liquid crystal projector apparatus according to an eighth
embodiment of the present invention;
[0060] FIGS. 24A, 24B are perspective views each illustrating part
of the liquid crystal unit and liquid crystal unit cooling system
in the liquid crystal projector apparatus according to the eighth
embodiment of the present invention; and
[0061] FIG. 25 is a perspective view illustrating part of a liquid
crystal unit and a liquid crystal unit cooling system in a liquid
crystal projector apparatus according to a ninth embodiment of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0062] FIG. 6 is a perspective view illustrating an optical system
and a liquid crystal unit cooling system extracted from a liquid
crystal projector apparatus according to a first embodiment of the
present invention. FIG. 7 is a perspective view of the liquid
crystal projector apparatus illustrated in FIG. 6, taken from
another direction. FIG. 8 is an exploded perspective view
illustrating part of the liquid crystal unit and liquid crystal
unit cooling system in the liquid crystal projector apparatus
illustrated in FIG. 6. FIG. 9 is a front view of the liquid crystal
unit and liquid crystal unit cooling system illustrated in FIG. 8.
FIG. 10 is a plan view illustrating the internal structure of a
heat exchanger for the liquid crystal projector apparatus
illustrated in FIG. 6.
[0063] Referring first to FIGS. 6 and 7, liquid crystal unit
cooling system 32a comprises liquid crystal unit 23 and liquid
cooling module 33a.
[0064] Liquid crystal unit 23, as illustrated in FIGS. 8 and 9 in
greater details, comprises liquid crystal panels 17a, 17b, 17c
corresponding to the respective color light; incident side
polarizing plates 18a, 18b, 18c; exit side polarizing plates 19a,
19b, 19c; color combiner prism 15; and first holder member 34a for
integrally holding these components. Liquid crystal panels 17a,
17b, 17c, incident side polarizing plates 18a, 18b, 18c, and exit
side polarizing plates 19a, 19b, 19c are disposed in correspondence
to incident planes of the respective color light associated
therewith, and are common to those used in conventional liquid
crystal projector apparatuses. Each of liquid crystal panels 17a,
17b, 17c has a flexible printed circuit board (hereinafter called
"FPC 25a, 25b, 25c") attached thereto for providing signal lines
for controlling the liquid crystal panel. Projection lens 16 is
connected to liquid crystal unit 23 for projecting a light flux
combined by color combiner prism 15 as an image. In the following
description, when reference is made to structure members of liquid
crystal unit 23, the structure members mean liquid crystal panels
17a, 17b, 17c, incident side polarizing plates 18a, 18b, 18c, exit
side polarizing plates 19a, 19b, 19c, and color combiner prism
15.
[0065] First holder member 34a for holding liquid crystal unit 23
is made of a material which excels in thermal conductivity and has
high workability, for example, aluminum, magnesium alloy, and the
like, and comprises holding mechanism 51a for integrally fixing the
structure members of liquid crystal unit 23 at predetermined
positions. First holder member 34a is disposed in close proximity
to and thermally connected to first heat exchanger 36a, later
described, on the surface opposite to that for holding liquid
crystal panels 17a, 17b, 17c, incident side polarizing plates 18a,
18b, 18c, and exit side polarizing plates 19a, 19b, 19c.
[0066] Holding mechanism 51a can be comprised, for example, of a
fixing groove, a holding plate, or the like, but not limited
thereto, and any mechanism may be used as long as it can securely
fixes the structure members of liquid crystal unit 23, and
thermally connects with first holder member 34a and first heat
exchanger 36a. The contact surface of holding mechanism 51 with the
structure members of liquid crystal unit 23 may be provided with a
thermal interface such as a high thermally conductive sheet,
silicone grease, a phase change sheet, or the like to reduce a
contact heat resistance.
[0067] Liquid cooling module 33a comprises water distributing pump
35 for circulating coolant liquid 31; first heat exchanger 36a
connected to an object to be cooled for receiving heat therefrom;
reservoir tank 40 for guaranteeing a certain amount of the coolant
liquid and accommodating variations in volume due to thermal
expansion; and radiator 50 for cooling heated coolant liquid
31.
[0068] Water distributing pump 35 used herein, which forms part of
liquid cooling module 33a, may be a centrifugal pump or a
piezoelectric pump. Water distributing pump 35 is connected to
first heat exchanger 36a through a pipe.
[0069] As illustrated in FIG. 10, first heat exchanger 36a is
provided with first channel 55a formed therein for passing coolant
liquid 31 therethrough. First channel 55a is formed such that
coolant liquid 31, which has entered from an inlet port,
sequentially flows through heat receiving surfaces 56a positioned
in opposition to the respective color liquid crystal panels.
[0070] Radiator 50 is disposed at a location downstream of first
heat exchanger 36a. Radiator 50 comprises heat sink 53 and air
cooling fan 54. Heat sink 53 has a radiator internal channel (not
shown) formed therein for passing coolant liquid 31 therethrough,
and is also formed with a number of fins extending therefrom. Air
cooling fan 54 is positioned near the fins for promoting the
cooling of coolant liquid 31.
[0071] Reservoir tank 40 is disposed at a location downstream of
radiator 50. Reservoir tank 40 compensates for a loss of the
coolant liquid due to a coolant leak (evaporation) from holes of
fibers of resin pipes used at pipe connections, and accommodates
variations in volume of coolant liquid 31 due to thermal expansion
to prevent damages to the pipe, lowered liquid feeding capabilities
of water distributing pump 35 due to the introduction of air
bubble, and clogging of the pipe. Reservoir tank 40 has an outlet
port connected to water distributing pump 35 to form a closed loop
as a whole. The position of reservoir tank 40 is not limited to a
location downstream of radiator 50, but may be determined as
appropriate in consideration of the overall layout.
[0072] For coolant liquid 31, a anti-freeze solution is preferably
used, such as propylene alcohol, propylene glycol, and the
like.
[0073] Next, description will be made on the cooling operation of
liquid crystal unit 23.
[0074] Liquid crystal unit 23 integrally held by first holder
member 34a generates heat through absorption of transmitted light
in operation. The generated heat is transferred to first holder
member 34a through holding member 51a. The sources of the heat are
incident side polarizing plates 18a, 18b, 18c, exit side polarizing
plates 19a, 19b, 19c, and liquid crystal panels 17a, 17b, 17c, and
heat generated by these components is collectively transferred to
first holder member 34a.
[0075] On the other hand, coolant liquid 31 is fed to first heat
exchanger 36a by water distributing pump 35. Coolant liquid 31
dissipates the heat generated in liquid crystal unit 23 through
first holder member 34a within first heat exchanger 36a. More
specifically, heat transferred from liquid crystal unit 23 to first
holder member 34a is transported from the surface of first heat
exchanger 36a to coolant liquid 31 through heat receiving surface
56a. Coolant liquid 31, which is heated through heat exchange, is
exhausted from the outlet port of first heat exchanger 36a, and fed
to radiator 50. As coolant liquid 31 circulates along the internal
channel within radiator 50, coolant liquid 31 is cooled down by
heat sink 53 and air cooling fan 54, and returns to water
distribution pump 35 via reservoir tank 40. The foregoing actions
are repeated to eventually emit the heat generated in liquid
crystal unit 34 to the atmosphere through coolant liquid 31.
[0076] While the temperature of coolant liquid 31 depends on the
outside air temperature, an example is shown below. For example,
when the outside air temperature is 30.degree. C., coolant liquid
31 is normally at about 40.degree. C. when it flows into first heat
exchanger 36a, and is heated to as high as 50.degree. C. to
60.degree. C., after it has received the heat, depending on the
amount of heat generated by liquid crystal unit 23. Coolant liquid
31 radiates the heat through radiator 50, and cools down
substantially to the outside air temperature (35-40.degree. C.
depending on the capacity of radiator 50). The temperature on the
heat receiving surface 56a of first heat exchanger 36a is
approximately 40.degree. C., though it depends on the temperature
of coolant liquid 31.
[0077] As described above, since the liquid projector apparatus of
this embodiment employs a liquid cooling scheme, it does not suffer
a degraded image quality due to dust particles, which can cause a
problem in an air cooling scheme. Also, the liquid projector
apparatus of this embodiment is advantageous in providing silenced
operation because it requires only a small fan. Further, since the
cooling structure is disposed independently of the liquid crystal
unit, the liquid crystal projector apparatus of this embodiment can
provide images of high quality because the functions of the liquid
crystal unit is less affected by the cooling structure.
[0078] Next, a liquid crystal projector apparatus according to a
second embodiment of the present invention will be described with
reference to FIGS. 11A, 11B, 12. FIGS. 11A, 11B are perspective
views each illustrating part of a liquid crystal unit and a liquid
crystal unit cooling system in a liquid crystal projector apparatus
according to the second embodiment of the present invention. FIG.
11A is a perspective view of an assembled liquid crystal unit
cooling system, and FIG. 11B illustrates an exploded perspective
view of the liquid crystal unit cooling system. FIG. 12 is a front
view of the liquid crystal unit and liquid crystal unit cooling
system in the liquid crystal projector apparatus illustrated in
FIGS. 11A, 11B.
[0079] Liquid crystal unit cooling system 32b in the liquid crystal
projector apparatus according to the second embodiment differs from
the first embodiment in that a pair of holder member and heat
exchangers are disposed on the upper and lower sides of the liquid
crystal unit, and is similar to the first embodiment in the
remaining aspects.
[0080] First holder member 34b and second holder member 34c are
disposed, respectively on the lower and upper sides of liquid
crystal unit 23. First holder member 34b and second holder member
34c are connected to first heat exchanger 36b and second heat
exchanger 36c, respectively. First holder member 34b, second holder
member 34c, first heat exchanger 36b, and second heat exchanger 36c
are similar in structure to first holder member 34a and first heat
exchanger 36a, respectively, illustrated in the first embodiment.
Liquid crystal unit 23 is securely held by similar holding
mechanisms 51b, 51c, and first holder member 34b and second holder
member 34c are thermally connected to first heat exchanger 36b and
second heat exchanger 36c, respectively. A piping configuration for
connecting first heat exchanger 36b and second heat exchanger 36c
to water distributing pump 35 and radiator 50 is also modified from
the first embodiment, though not shown. The rest of the structure
in the second embodiment is similar to the first embodiment, and
second heat exchanger 36c is also provided with a second channel
(not shown) formed therein, similar to that in first heat exchanger
36b. In FIGS. 11A, 11B, FPC 25 extends through second holder member
34c and second heat exchanger 36c, the reason for which will be
described later in connection with a fourth embodiment.
[0081] With the foregoing structure, heat generated in liquid
crystal unit 23 is transferred to first holder member 34b and
second holder member 34c through holding structures 51b, 51c, and
is dissipated by a pair of first heat exchanger 36b and second heat
exchanger 36c through heat receiving surfaces 56b and 56c (not
shown).
[0082] By thus cooling the liquid crystal unit simultaneously from
the upper and lower sides, the liquid crystal projector apparatus
can further improve the liquid crystal unit cooling capabilities to
keep the liquid crystal unit at a low temperature, and can
substantially uniformly maintain temperature distributions on
optically transparent surfaces of the liquid crystal panels and
polarizing plates to accomplish a high quality of projected images
with less color shading.
[0083] Next, a liquid crystal projector apparatus according to a
third embodiment of the present invention will be described with
reference to FIG. 13. FIG. 13 is a side view illustrating part of a
liquid crystal unit in a liquid crystal projector apparatus
according to the third embodiment of the present invention. It
should be understood that the following description is made in
connection with liquid crystal panel 17c for blue light, given as
an example, but can be applied to liquid crystal panels of the
other colors.
[0084] As described in "Description of the Related Art," liquid
crystal projector apparatuses are often provided with an adjusting
mechanism (optical axis adjustment) for adjusting a liquid crystal
panel, which forms part of a liquid crystal unit, in the vertical,
horizontal, and rotating directions for adjusting the registration.
The third embodiment can be applied to such a liquid crystal
projector apparatus. As illustrated in FIG. 13, liquid crystal
panel 17c is supported at a distance from color combiner prism 15.
Liquid crystal panel 17c is securely held by fixture 26c, and
fixture 26c is supported by holder protrusions 27 at four points,
i.e., at four corners thereof, and securely adhered after the
optical axis has been adjusted.
[0085] The third embodiment is characterized in that thermally
conductive flexible sheet 28a is applied to fixture 26 to which
liquid crystal panel 17c is fixed, a distal end of thermally
conductive flexible sheet 28a is connected to first holder member
34a. Thermally conductive sheet 28a can be made, for example, of a
one-side adhesive graphite sheet of approximately 100 .mu.m
thick.
[0086] With the foregoing structure, liquid crystal panel 17c can
be thermally connected to and cooled down by first holder member
34a which has a heat absorbing function, without affecting a
posture in which liquid crystal panel 17c is fixed in the air. In
other words, the heat can be efficiently absorbed by first holder
member 34a without damaging the alignment of liquid crystal panel
17c, thus resulting in improved capabilities of cooling liquid
crystal panel 17c, a limited panel temperature, and a longer
lifetime. Also, the temperature distribution on the panel surface
is made uniform to help improve the quality of projected
images.
[0087] The third embodiment is not limited to the one illustrated
in FIG. 13, but thermally conductive flexible sheets 28a, 28b,
similar to that shown in FIG. 13 may be applied to the front and
rear surfaces (incident side and exit side) of liquid crystal panel
17c, for example, as illustrated in FIGS. 14A, 14B. Here, FIG. 14A
is a side view illustrating a part of the liquid crystal panel
extracted from the liquid crystal projector apparatus, and FIG. 14B
is a perspective view illustrating part of the liquid crystal
panel. The embodiment illustrated in FIGS. 14A, 14B can more
effectively cool down liquid crystal panel 17c particularly when
liquid crystal panel 17c has a remarkable temperature gradient in
the thickness direction, because the heat can be absorbed from the
front and back surface of liquid crystal panel 17C. Also, the
thermally conductive sheets may be disposed to connect to second
holder member 34c on the upper side of liquid crystal unit 23, as
previously described in the second embodiment.
[0088] Next, a liquid crystal projector apparatus according to a
fourth embodiment of the present invention will be described with
reference to FIGS. 15A-17C. The fourth embodiment is applied in
combination with the second embodiment described above. FIG. 15A is
a side view illustrating part of a liquid crystal unit according to
the fourth embodiment, and FIG. 15B is a partially enlarged side
view of part indicated by A in FIG. 15A. FIG. 15C is a perspective
view illustrating part of the liquid crystal unit and liquid
crystal unit cooling system according to the fourth embodiment.
FIGS. 16A-16C illustrate a full view of a holder member, while
FIGS. 17A-17C illustrate a full view of a heat exchanger.
Specifically, FIGS. 16A, 17A illustrate perspective views taken
from the upper surface; FIGS. 16B, 17B back views; and FIGS. 16C,
17C top plan views, respectively.
[0089] In FIGS. 15A, 15B, thermally conductive flexible sheets 28a,
28b are each applied to a lower portion of the front or back
surface of liquid crystal panel 17c. Simultaneously, thermally
conductive sheet 28c is also applied to an upper portion of one
surface of liquid crystal panel 17c. Thermally conductive sheets
28a, 28b have their distal ends connected to first holder member
34b, while thermally conductive sheet 28c has its distal end
connected to second holder member 34c.
[0090] As illustrated in FIGS. 16A-16C, in a pair of holder members
for holding liquid crystal unit 23 from above and from below,
second holder member 34c, to which FPCs 25a, 25b, 25c extends, is
formed with through holes 29a, 29b, 29c at positions at which FPCs
25a, 25b, 25c extend through second holder member 34c. Also, as
illustrated in FIGS. 17A-17C, in a pair of the upper and lower heat
exchangers, second heat exchanger 36c, to which FPCs 25a, 25b, 25c
extend, is formed with throughholes 29a', 29b', 29c' at positions
at which FPCs 25a, 25b, 25c extend through second heat exchanger
36c. As illustrated in portion A in FIG. 15C, FPCs 25a, 25b, 25c
extend upward through these throughholes (only FPC 25c is shown in
FIG. 15C).
[0091] Thermally conductive sheet 28c on the upper side of liquid
crystal unit 23 is once guided upward from FPC throughholes 29c,
29c', which extend through holder member 34c and second heat
exchanger 36c, respectively, and is connected to the upper surface
(on the back side when viewed from liquid crystal unit 23) of
second heat exchanger 36c.
[0092] FIG. 17B illustrates the channel arrangement in a jacket.
Since the channel of second heat exchanger 36c is formed to avoid
interference with the respective FPC throughholes, the channels of
first lower heat exchanger 36b and second upper heat exchanger 36c
are not routed in mirror symmetry. In other words, as is apparent
from a comparison with FIG. 10, the upper and lower heat exchangers
differ in the rooting of channel from each other.
[0093] While thermally conductive sheet 28c on the upper surface is
applied only on the exit surface of the liquid crystal panel, it
should be understood that thermally conductive sheet 28c can be
applied on the incident surface of the liquid crystal panel in a
manner similar to thermally conductive sheet 28b on the lower
surface.
[0094] In this way, even when FPC 25 projects upward, FPC 25 can be
connected to an external control board (not shown) without
interfering with the holder member or heat exchangers. When
thermally conductive sheet 28c does not interfere with FPC 25,
thermally conductive sheet 28c may be connected directly to second
holder member 34c, without extending a throughhole.
[0095] Next, a liquid crystal projector apparatus according to a
fifth embodiment of the present invention will be described with
reference to FIGS. 18A-18C. FIGS. 18A-18C illustrate a liquid
crystal panel in the liquid crystal projector apparatus according
to the fifth embodiment, wherein FIG. 18A is a side view of the
liquid crystal panel before a transparent thin plate member is
attached; FIG. 18B is a perspective view of the liquid crystal
panel illustrated in FIG. 18A; and FIG. 18C is a perspective view
of the liquid crystal panel after the transparent thin plate member
has been attached thereto. While the following description will be
made on a liquid crystal panel 17a for red light, given as an
example, it should be understood that the description can be
applied to the liquid crystal panels of the other colors.
[0096] As illustrated in FIGS. 18A-18C, transparent thin plate
members 38a, 38b, each having a thermal conductivity larger than
panel component member 37 of liquid crystal panel 17a, are bonded
on both of an incident side panel surface and an exit side panel
surface of liquid crystal panel 17a which forms part of liquid
crystal unit 23. The transparent thin plate member may be applied
to only one of the incident and exit side panel surfaces.
[0097] Transparent thin plate members 38a, 38b may be members which
excite a thermal diffusion on the panel surfaces of liquid crystal
panel 17a, i.e., transparent members having a higher thermal
conductivity than panel component member 37 from a viewpoint of
thermal characteristics. Conventionally, when a heat dissipating
plate having a high thermal conductivity is bonded to a liquid
crystal panel for improving the cooling capabilities of the liquid
crystal panel itself, the heat dissipating plate is limited to a
sapphire substrate, which is disadvantageous in cost. This
embodiment can utilize, for example, a quartz substrate which has a
high thermal conductivity and good workability, and is less
expensive than the sapphire substrate. Alternatively, any other
transparent sheet member may be utilized on the condition that it
provides predetermined thermal characteristics.
[0098] Since the transparent thin plate members 38a, 38b contribute
to an increased thermal diffusion on the panel surfaces, and to a
more averaged temperature distribution within the panel surfaces of
liquid crystal panel 17a, a maximum temperature can be reduced
within the panel surfaces of the liquid crystal panel 17a to
suppress local temperature rises. Furthermore, the temperature on
the outer periphery of the panel surface of liquid crystal panel
17a rises due to the thermal diffusion to increase a difference in
temperature between liquid crystal panel 17a and first holder
member 34a, thus further promoting the heat exchange between the
outer periphery of liquid crystal panel 17a and first holder member
34a to reduce an average temperature of liquid crystal panel 17a as
well. The thermally conductive flexible sheet detailed in the third
embodiment may be attached around the panel surface such that the
heat is absorbed by the holder member, to provide similar
advantages.
[0099] Next, a liquid crystal projector apparatus according to a
sixth embodiment of the present invention will be described with
reference to FIGS. 19A-19C. FIGS. 19A-19C illustrate an exit side
polarizing plate of the liquid crystal projector apparatus
according to the sixth embodiment, wherein FIG. 19A is a
perspective view of the exit side polarizing plate before a sheet
member is attached thereto; FIG. 19B a perspective view of the exit
side polarizing plate after the sheet member has been attached
thereto; and FIG. 19C a perspective view of the exit side
polarizing plate when it is mounted on a holder member. While the
following description will be made on exit side polarizing plate
19b for green light, given as an example, it should be understood
that the description can also be applied to the exit side
polarizing plates of the other colors and incident side polarizing
plates.
[0100] Exit side polarizing plate 19b is comprised of glass
substrate 39 and polarizing film 41. Polarizing film 41 is adhered
to a central region of glass substrate 39, such that an outer
peripheral region of glass substrate 39 lacks polarizing film 41.
Sheet member 42 having a thermal conductivity larger than glass
substrate 39 is applied to the outer peripheral region of glass
substrate 39 lacking polarizing film 41. Sheet member 42 used
herein may be, for example, a single-side adhesive thermally
conductive sheet such as a graphite sheet illustrated in the third
embodiment. Since sheet member 42 is adhered around polarizing film
41, it need not be transparent but preferably does not excite stray
light. Also, while sheet member 42 may be adhered on either the
incident side surface or exit side surface of exit side polarizing
plate 19b, sheet member 42 is preferably adhered to the side that
is pressed against holding mechanism 51d of first holder member
34a.
[0101] Thus, similar to the fifth embodiment, the exit side
polarizing plate of the sixth embodiment contributes to improved
thermal diffusion performance on the surface of glass substrate 39,
an averaged temperature distribution within the surface of glass
substrate 39 including polarizing film 41, and a reduction in a
maximum temperature of polarizing film 41. Also, since the
temperature rises around polarizing film 41, i.e., in the outer
peripheral region of glass substrate 39, to which sheet member 42
has been adhered, this rise in temperature promotes the absorption
of heat to first holder member 34a through holding mechanism 51d.
Moreover, since sheet member 42 adhered around polarizing film 41
intervenes on the surface of polarizing plate 19b connected to
holding mechanism 51d, a contact thermal resistance is reduced
between exit side polarizing plate 19b and first holder member 34a,
thus further improving the heat absorption efficiency.
Consequently, an average temperature of polarizing film 41 also
becomes lower to further prolong the lifetime of the polarizing
plate.
[0102] Next, a liquid crystal projector apparatus according to a
seventh embodiment of the present invention will be described with
reference to FIG. 20. FIG. 20 is a plan view illustrating the
internal structure of a heat exchanger in a liquid crystal
projector apparatus according to the seventh embodiment of the
present invention.
[0103] First heat exchanger 36d in this embodiment has inlet port
43a and outlet port 44a of first channel 55c both positioned closer
to projection lens 16, and U-shaped first channel 55c formed with
inlet port 43a positioned closer to a blue light liquid crystal
panel (labeled B in FIG. 20) and outlet port 44a positioned closer
to a red light liquid crystal panel (labeled R in FIG. 20) (in the
following description on the seventh embodiment, the liquid crystal
panel includes an incident side polarizing plate and an exit side
polarizing plate). A green light liquid crystal panel (labeled G in
FIG. 20) is positioned halfway between the red and blue light
liquid crystal panels. Consequently, the liquid crystal panels are
cooled down as a whole in the order of the blue, green, and red
light liquid crystal panels.
[0104] The channel is routed in the foregoing manner for the reason
set forth below. Since light energy is generally stronger at a
shorter wavelength, in a light modulator in a three-plate type
liquid crystal projector apparatus, the blue light optical element
(polarizing plates and liquid crystal panels) tends to experience
the largest heat caused by light absorbed by optical elements, the
green light optical element tends to receive the next largest
amount of light. Unbalanced temperature characteristics among the
liquid crystal panels of the respective color light cause a change
in operating speed characteristics of the liquid crystal materials,
and also cause a degraded quality of images displayed at high
speeds due to variations in display speed among R, G, B. Likewise,
in regard to the polarizing plates, a unit replacement time
(lifetime) is determined by the member which experiences the
highest temperature, leading to a requirement for maintaining the
temperature characteristics of the light modulators corresponding
to the respective color lights as constant as possible. Bearing the
foregoing in mind, in first heat exchanger 36d which connects a
holder member mounted with liquid crystal unit 23, first channel
55c is routed such that coolant liquid 31 flows into first channel
55c from a position corresponding to the blue light liquid crystal
panel, passes through a position corresponding to the green light
liquid crystal panel, and finally flows out from a position
corresponding to the red light liquid crystal panel to circulate to
a liquid cooling module heat dissipator (not shown).
[0105] With first channel 55c thus routed, coolant liquid 31 at a
low temperature is supplied to the blue light liquid crystal unit
which is more heated immediately after it has been introduced into
first channel 55c, and the red light liquid crystal unit, which
generates a relatively small amount of heat is cooled by coolant
liquid 31 at a higher temperature after it has received the heat,
thereby taking the balance between the heat generation and cooling
of the respective color liquid crystal units.
[0106] Alternatively, as illustrated in FIG. 21, inlet port 43b and
outlet port 44b of first channel 55d may be disposed on the left
and right sides of projection lens 16, wherein similarly, inlet
port 43b is positioned closer to a blue liquid crystal panel
(labeled B in FIG. 21), and outlet port 44b is positioned closer to
a red liquid crystal panel (labeled R in FIG. 21) to form first
channel 55d generally routed in T-shape.
[0107] Further alternatively, as illustrated in FIG. 22, first
channel 55e may be routed such that its width is set widest (WB) at
a position corresponding to a blue liquid crystal panel and
incrementally narrower toward a position corresponding to a green
liquid crystal panel (WG) and a position corresponding to a red
liquid crystal panel (WR). Such a setting of the channel width is
particularly effective when the liquid crystal units corresponding
to the respective color light largely vary in the amount of heat
generated thereby. The area of the coolant circulating channel
(i.e., an area over which heat is absorbed by the coolant) is set
wider at the position corresponding to the blue liquid crystal
unit, which will reach a higher temperature, to allocate larger
cooling capabilities (jacket heat receiving capabilities). The
channel width ratio (WB:WG:WR) or channel area ratio is determined
in accordance with a heat generation ratio of the liquid crystal
panels of the respective color light.
[0108] The foregoing embodiment can be applied in a similar manner
to second heat exchanger 36c disposed on the upper side of liquid
crystal unit 23, described in the second embodiment.
[0109] Next, a liquid crystal projector apparatus according to an
eighth embodiment of the present invention will be described with
reference to FIGS. 23A-23C. The liquid crystal projector apparatus
according to the eighth embodiment can be applied when the liquid
crystal units are cooled down to a room temperature or lower with
the intention to further prolong the lifetime of the liquid crystal
units. FIGS. 23A and 23B are a perspective view and a side view,
respectively, illustrating part of the liquid crystal unit and
liquid crystal unit cooling system in the liquid crystal projector
apparatus according to the eighth embodiment. FIG. 23C in turn is
an exploded perspective view of part of the liquid crystal unit and
liquid crystal unit cooling system illustrated in FIG. 23A.
[0110] The eighth embodiment features in that Peltier element 45a
is sandwiched between first holder member 34a for holding liquid
crystal unit 23 and first heat exchanger 36a, with its lower
temperature side directed to the surface of first holder member
34a. First holder member 34a connected to heat absorbing surface
46a of Peltier element 45a is cooled down to an outside air
temperature or lower, while first heat exchanger 36a connected to
heat generating surface 47a of Peltier element 45a receives heat
generated by the thermoelectric element. Then, the heat of first
heat exchanger 36a is eventually radiated by a radiator (not shown)
of a liquid cooling module through coolant liquid 31.
[0111] The temperature on the heat absorbing surface of Peltier
element 45a is preferably set within a temperature range (>dew
point) in which no condensation occurs on the thermoelectric
elements or optical elements, and countermeasures are preferably
taken against condensation when liquid crystal unit 23 must be
cooled down to a temperature below that temperature range. In
addition, the temperature on the heat generating surface of Peltier
element 45a is preferably set at the boiling point of coolant
liquid 31 or lower (120.degree. C.).
[0112] Generally, a liquid crystal unit cooling structure cannot
cool down the temperature of a heat exchanger to an outside air
temperature or lower due to a heat transportation process of a
liquid cooling module. As described above, the temperature on the
heat receiving surface of the heat exchanger can be cooled down to
approximately 40.degree. C., for example, when the outside air
temperature is 30.degree. C., and the temperature of liquid crystal
unit 23 is dominated by this jacket surface temperature. However,
the use of the Peltier element enables liquid crystal unit 23 to be
cooled down to the outside air temperature or lower.
[0113] FIGS. 24A, 24B illustrate a liquid crystal projector
apparatus in which Peltier elements are applied to the liquid
crystal cooling structure shown in the aforementioned second
embodiment. A pair of Peltier elements 45a, 45b are bonded between
each of a pair of first holder member 34b and second holder member
34c for holding liquid crystal unit 23 from above and from below
and each of a pair of first lower heat exchanger 36b and second
upper heat exchanger 36c corresponding to first and second holder
members 34b, 34c, such that each of Peltier elements 45a, 45b has
its lower temperature side directed to the surface of associated
holder member 34b, 34c.
[0114] With the foregoing structure, the pair of first lower holder
member 34b and second upper holder member 34c connected to heat
absorbing surfaces 46a, 46b of Peltier elements 45a, 45b are cooled
down to an outside air temperature or lower, and heat generated by
the thermoelectric elements is received by the pair of first heat
exchanger 36b and second heat exchanger 36c connected to heat
generating surfaces 47a, 47b, and coolant liquid 31 can be cooled
down by a radiator (not shown) of the liquid cooling module.
[0115] As described above, by using a liquid crystal unit cooling
structure employing Peltier elements, it is possible to largely
reduce an operating temperature of the liquid crystal units and
further prolong the lifetime of the liquid crystal units.
[0116] Next, a liquid crystal projector apparatus according to a
ninth embodiment of the present invention will be described with
reference to FIG. 25. The liquid crystal projector apparatus
according to the ninth embodiment can be used to more thoroughly
prevent dust particles from introducing into a liquid crystal units
etc. FIG. 25 is a perspective view illustrating part of a liquid
crystal unit and a liquid crystal unit cooling system of the liquid
crystal projector apparatus, taken from the back side.
[0117] The liquid crystal projector apparatus of the ninth
embodiment is characterized in that an optical engine represented
by the liquid crystal unit, i.e., the optical engine comprised of
illumination optical system 2, color separating optical system 7,
and light composing optical system 13 illustrated in FIG. 1, are
installed in a sealed structure.
[0118] Optical system holder member 48 holds and fixes a
multiplicity of lenses and mirrors, which make up the optical
engine, and sealingly encloses these components of the optical
engine to form an isolated space within the housing of liquid
crystal projector apparatus 1. The bottom surface of optical system
holder member 48 partially includes holder member 34a. Therefore,
liquid crystal unit 23 is cooled down in a manner similar to that
shown in the first embodiment, i.e., by absorbing generated heat
into first holder member 34a through solid heat conduction, and
emitting the heat to the outside through coolant liquid 10 from
radiator 50 by way of first heat exchanger 36a.
[0119] In the ninth embodiment, the optical engine is sealed by
optical system holder member 48 such that liquid crystal unit 23
can be cooled down while it is substantially isolated from air
circulating within the housing, even when external air is
introduced into the housing in a manner similar to the prior art
for purposes of cooling a power supply, substrates, lamp, and the
like. The foregoing structure can block dust particles which would
otherwise introduce into liquid crystal unit 23, thereby making it
possible to provide a liquid crystal projector apparatus which
excels more in reliability. It should be understood that the ninth
embodiment can be applied as appropriate in combination with the
aforementioned second to eighth embodiments.
[0120] While detailed description on the respective embodiments has
been made above in connection with a liquid cooling scheme, the
liquid crystal projector apparatus of the present invention is not
limited to the liquid cooling scheme, but can also employ, for
example, an air cooling scheme.
[0121] In the air cooling scheme, an air cooling unit in a simple
structure can be employed with an aluminum heat sink connected to a
heat absorbing holder in place of a water cooling jacket for
dissipating heat. The "air cooling unit" used herein does not refer
to a structure for feeding air to a liquid crystal unit itself as
in the prior art, but to design the first heat exchanger and second
heat exchanger themselves using the air cooling scheme. For
example, in a radiator of a popularly-priced projector which is
required to be small in size and low in cost but provides a low
luminance and generates a small amount of heat, an air cooling unit
which has a small heat radiation capacity may be replaced for a
liquid cooling unit.
[0122] Further, the present invention can also be applied
completely in a similar manner to a single-plate type liquid
crystal panel, i.e., a liquid crystal projector apparatus which
comprises a single liquid crystal panel that has a color filter
which passes predetermined color light therethrough separately for
each of cells which make up the liquid crystal panel.
[0123] While certain preferred embodiments of the present invention
have been shown and described in detail, it should be understood
that various changes and modifications may be made without
departing from the spirit or scope of the appended claims.
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